Thermoplastic elastomeric compositions and method for their preparation

Abstract

Thermoplastic elastomeric compositions of improved properties are prepared by cross-linking an ethylene/α,β-unsaturated carboxylic acid, ester, or anhydride copolymer in the presence of a polyolefin using an epoxy compound catalyzed with a tertiary amine.

I claim: 
     
       1. A thermoplastic elastomer composition comprising: (a) between about 5 and 95 weight % of at least one ethylene-vinyl acetate-maleic anhydride terpolymer having a number average molecular weight of about 1,000 to 1,000,000 g/mol; and   (b) between about 5 and 95 weight % of at least one polyolefin; wherein (a) has been crosslinked in situ using an epoxy compound catalyzed with a tertiary amine and said composition is in the form of a substantially uniform dispersion of small particles of (a) in the polyolefin matrix of (b).     
     
     
       2. The composition according to claim 1 wherein (b) is selected from polymers and copolymers of alpha olefins having from 2 to 10 carbon atoms. 
     
     
       3. The composition according to claim 2 wherein said ethylene-vinyl acetate-maleic anhydride terpolymer is present in the composition as particles having an average particle size below about 50 μm in an amount between about 20 and 80 weight % based on the total of (a) and (b) and contains at least about 55 mol % ethylene repeating units, up to 40 mol % vinyl acetate repeating units, and up to 5 mol % maleic anhydride repeating units and the polyolefin of (b) is selected from polyethylenes, polypropylenes, ethylene-alpha-olefin copolymers, propylene-alpha-olefin copolymers and mixtures thereof. 
     
     
       4. The composition according to claim 3 wherein the polyolefin of (b) has a flow rate of 0.1 to 20 grams/10 minutes at 230° C. and is selected from: polypropylene and copolymers of polypropylene in which propylene is the major monomer; and polyethylene and copolymers of polyethylene in which ethylene is the major monomer. 
     
     
       5. The composition according to claim 4 wherein said polyolefin of (b) is selected from isotactic polypropylene and a mixture of isotactic polypropylene and an ethylene-propylene copolymer. 
     
     
       6. The composition according to claim 5 wherein said polyolefin has a flow rate of 1 to 10 grams/10 minutes at 230° C. 
     
     
       7. The composition according to claim 3 wherein the terpolymer is present in the composition in an amount between about 40 and 60 weight % and contains between about 10 and 40 mol % vinyl acetate repeating units, between about 0.5 and 3 mol % maleic anhydride repeating units, the remainder being ethylene repeating units. 
     
     
       8. The composition according to claim 7 wherein the terpolymer contains between about 30 and 40 mol % vinyl acetate repeating units, between about 0.8 and 2 mol % maleic anhydride repeating units and the remainder being ethylene repeating units. 
     
     
       9. The composition according to claim 2 wherein said ethylene-vinyl acetate-maleic anhydride terpolymer is a mix of both low and high molecular weight terpolymer; wherein the low molecular weight terpolymer has a number average molecular weight between about 500 and 10,000 g/mol and a viscosity at 150° C. between 150 and 100,000 cP and the high molecular weight terpolymer has a melt index at 190° C. between about 5 and 300 grams/10 minutes and a number average molecular weight between about 25,000 and 1,000,000 g/mol. 
     
     
       10. The composition according to claim 9 wherein said low molecular weight terpolymer has viscosity at 150° C. between 1,000 and 10,000 cP, and said high molecular weight terpolymer has a melt index at 190° C. between about 5 and 20 grams/10 minutes and said number average molecular weight is between about 50,000 and 500,000 g/mol. 
     
     
       11. A cross-linkable composition comprising: (a) between about 5 and 95 weight % based on the total of (a) and (b) of at least one ethylene-vinyl acetate-maleic anhydride terpolymer having a number average molecular weight of about 1,000 to 1,000,000 g/mol;   (b) between about 5 and 95 weight % based on (a) and (b) of at least one polyolefin;   (c) about 1 to 20 parts per 100 parts (a) OF AT LEAST ONE EPOXY OF THE FORMULA, ##STR5##  in which n is between 2 and 6 inclusive, A is a polyfunctional group of the valency of n, and R is a hydrocarbon radical or hydrogen; and   (d) at least one tertiary amine wherein the ratio of epoxy to tertiary amine is about 1000:1 to 1:1.   
     
     
       12. The composition according to claim 11 wherein (b) is selected from polymers and copolymers of alpha olefins having from 2 to 10 carbon atoms. 
     
     
       13. The composition according to claim 12 wherein said ethylene-vinyl acetate-maleic anhydride terpolymer is present in the composition as particles having an average particle size below about 50 mm in an amount between about 20 and 80 weight % based on the total of (a) and (b) and contains at least about 55 mol % ethylene repeating units, up to 40 mol % vinyl acetate repeating units, and up to 5 mol % maleic anhydride repeating units and the polyolefin of (b) is selected from polyethylenes, polypropylenes, ethylene-alpha-olefin copolymers, propylene-alpha-olefin copolymers and mixtures thereof. 
     
     
       14. The composition according to claim 13 wherein said polyolefin of (b) is selected from isotactic polypropylene and a mixture of isotactic polypropylene and an ethylene-propylene copolymer. 
     
     
       15. The composition according to claim 12 wherein said ethylene-vinyl acetate-maleic anhydride terpolymer is a mix of both low and high molecular weight terpolymer; wherein the low molecular weight terpolymer has a number average molecular weight between about 500 and 10,000 g/mol and a viscosity at 150° C. between 150 and 100,000 cP and the high molecular weight terpolymer has a melt index at 190° C. between about 5 and 300 grams/10 minutes and a number average molecular weight between about 25,000 and 1,000,000 g/mol. 
     
     
       16. The composition according to claim 12 wherein the epoxy is present in an amount between 1 and 10 parts per hundred parts of ethylene-vinyl acetate-maleic anhydride terpolymer, n is 2, 3, or 4, A is a polyhydroxy group, and R is hydrogen. 
     
     
       17. The composition according to claim 11 wherein the tertiary amine is non-volatile at processing conditions and is present in a concentration per epoxy between about 1:100 and 1:10; the amount of epoxy is such that the equivalent ratio, ##EQU2## is between about 0.1 and 1. 
     
     
       18. The composition according to claim 17 wherein the amount of epoxy is such that the equivalent ratio is between about 0.5 and 1.0. 
     
     
       19. The composition according to claim 17 wherein the tertiary amine is selected from triethyl amine, tributyl amine, dimethylaniline, diazabicyclo[2.2.2]octane, and the epoxy is selected from polyglycidyl ethers of polyhydroxy compounds. 
     
     
       20. The composition according to claim 19 wherein the epoxy is selected from triglycidyl ethers of triols. 
     
     
       21. The composition according to claim 20 wherein the epoxy is Bisphenol-A diglycidyl ether. 
     
     
       22. A process for producing a thermoplastic elastomer comprising: (1) mixing (a) between about 5 and 95 weight % based on the total of (a) and (b) of at least one ethylene-vinyl acetate-maleic anhydride terpolymer having a number average molecular weight of about 1,000 to 1,000,000 g/mol;   (b) between about 5 and 95 weight % based on (a) and (b) of at least one polyolefin;   (c) about 1 to 20 parts per 100 parts (a) of at least one epoxy of the formula, ##STR6##  in which n is between 2 and 6, A is a polyfunctional group of the valency of n, and R is a hydrocarbon radical or hydrogen; and   (d) at least one tertiary amine wherein the ratio of epoxy to tertiary amine is about 1000:1 to 1:1, and     (2) heating this mixture at a sufficient temperature for a sufficient time to substantially cross-link (a), without substantial decomposition, and form a uniform dispersion of small particles of (a) in the polyolefin matrix.   
     
     
       23. The process according to claim 22 wherein steps (1) and (2) are conducted substantially at the same time. 
     
     
       24. The process according to claim 22 wherein (b) is selected from polymers and copolymers of alpha olefins having from 2 to 10 carbon atoms. 
     
     
       25. The process according to claim 24 wherein said ethylene-vinyl acetate-maleic anhydride terpolymer is present in the composition as particles having an average particle size below about 50 μm in an amount between about 20 and 80 weight % based on the total of (a) and (b) and contains at least about 55 mol % ethylene repeating units, up to 40 mol % vinyl acetate repeating units, and up to 5 mol % maleic anhydride repeating units and the polyolefin of (b) is selected from polyethylenes, polypropylenes, ethylene-alpha-olefin copolymers, propylene-alpha-olefin copolymers and mixtures thereof. 
     
     
       26. The process according to claim 25 wherein said polyolefin of (b) is selected from isotactic polypropylene and a mixture of isotactic polypropylene and an ethylene-propylene copolymer. 
     
     
       27. The process according to claim 24 wherein said ethylene-vinyl acetate-maleic anhydride terpolymer is a mix of both low and high molecular weight terpolymer; wherein the low molecular weight terpolymer has a number average molecular weight between about 500 and 10,000 g/mol and a viscosity at 150° C. between 150 and 100,000 cP and the high molecular weight terpolymer has a melt index at 190° C. between about 5 and 300 grams/10 minutes and a number average molecular weight between about 25,000 and 1,000,000 g/mol. 
     
     
       28. The process according to claim 22 wherein the epoxy is present in an amount between 1 and 20 parts per hundred parts of ethylene-vinyl acetate-maleic anhydride terpolymer, n is 2, 3, or 4, A is a polyhydroxy group, and R is hydrogen. 
     
     
       29. The process according to claim 22 wherein the tertiary amine is non-volatile at processing conditions and is present in a concentration per epoxy between about 1:100 and 1:10; the amount of epoxy is such that the equivalent ratio, Epoxide equivalents in the epoxy   Anhydride equivalents in the terpolymer is between about 0.1 and 1.   
     
     
       30. The process according to claim 29 wherein the amount of epoxy is such that the equivalent ratio is between about 0.5 and 1.0. 
     
     
       31. The process according to claim 29 wherein the tertiary amine is selected from triethyl amine, tributyl amine, dimethylaniline, diazabicyclo[2.2.2]octane, and the epoxy is selected from polyglycidyl ethers of polyhydroxy compounds. 
     
     
       32. The process according to claim 31 wherein epoxy is selected from triglycidyl ethers of triols. 
     
     
       33. The process according to claim 32 wherein the epoxy is bisphenol-A diglycidyl ether.